The effect of In doping on thermoelectric properties and phase transition of Zn4Sb3 at low temperatures

beta-Zn4Sb3 is a promising thermoelectric material for energy conversion applications due to its exceptional low thermal conductivity. In this report, the effect of In substitution on thermoelectric properties and beta to alpha/alpha' phase transition of indium doped compounds (Zn1-xInx) Sb-4(3) (x = 0-0.02) were investigated at temperatures from 5 to 310 K. The results indicated that low-temperature (T < 300 K) thermal conductivity. of the doped beta-(Zn1-x In-x)(4)Sb-3 (x not equal 0) reduced remarkably as compared with that of Zn4Sb3 presumably due to enhanced impurity (dopant) scattering of phonons. Direct current electrical resistivity rho and thermopower S were found to decrease and then increase moderately with the increase in the In content, which could be ascribed to the introduction of donors due to substitution of In3+ for Zn2+, leading to increased electron contribution. Moreover, it was found that the beta to alpha/alpha' phase transition of Zn4Sb3 was completely prohibited by In doping, implying that In was substituted predominantly for interstitial Zn and hindered their ordering. In addition, the thermoelectric figure of merit (= (ST)-T-2/rho lambda, where T is temperature) of the doped compound beta-(Zn1-xInx) Sb-4(3) ( x not equal 0) was smaller than that of Zn4Sb3 at the low temperatures because of substantial decrease in their thermopower, suggesting that In substitution for Zn in Zn4Sb3 is not beneficial for raising its low-temperature thermoelectric properties.